Electronic circuit designs are driven by various electrical signal parameters including information signal and noise signal specifications. In the course of conducting AC signal measurements on the performance of a circuit employing bipolar transistors, the operating point of a respective bipolar transistor is customarily predefined in terms of collector current (Ic) and collector-emitter voltage (Vce), as illustrated in the circuit schematic of FIG. 1. To establish these operating point conditions, a biasing circuit arrangement, such as that diagrammatically illustrated in FIG. 2, containing power supply voltage inputs and biasing resistors, through which the values of Ic and Vce are established, may be coupled to the transistor 11 of interest. In the non-limiting example of FIG. 2, the operating point of the transistor is established by coupling a collector bias supply voltage Vcc through a coupling resistor 13 to collector electrode 15, and coupling an emitter bias supply voltage Vee to emitter electrode 21. A further coupling resistor 23 may be coupled between collector electrode 15 and base electrode 25.
The value of the collector-emitter differential voltage Vce and the magnitude of collector current Ic are established by the values of Vcc, Vee and the bias resistors through which the power supply terminals of the biasing circuitry are coupled to the transistor. With such bias conditions established, an AC input signal waveform of interest may be applied to base electrode 25, and an output signal waveform measured at collector electrode 15, for example.
Because the operation of transistor 11 within the circuit of FIG. 2 depends upon the values of all of the components of the circuit, the measured performance values (e.g. characteristics of the output signal waveform at collector electrode 15) are necessarily affected by these biasing circuit components (power supply inputs and the coupling/biasing resistors). Due to this dependency, a custom bias circuit must be reconfigured each time a new transistor is to be evaluated, so that the measurement process is time consuming and computationally intensive. Indeed, even when successive transistors of the same type are to be tested, because the electronic parameters of each transistor are unique, the need to tailor the biasing components of the circuit for each performance measurement cannot be relaxed.